Most rickettsial pathogens are transmitted by ectoparasites such as fleas, lice, mites, and ticks during feeding or by scratching crushed arthropods or infectious feces into the skin. Inhaling dust or inoculating conjunctiva with infectious material may also cause infection. The specific vectors that transmit each form of rickettsiae are listed in Table 3-18. Transmission of some rickettsial diseases after transfusion or organ transplantation is rare but has been reported.